Method and equipment for making tension anchors



April 8, 1969 G. LAGERSTROM 3,436,923

METHOD AND EQUIPMENT FOR MAKING TENSION ANCHORS Filed July 7, 1966 Sheetof 4 I2 8 ll 5/ H I I INVENTOR. Gamma LnqcasTnB n BY April 1969 G.LAGERSTROM 3,436,923

METHOD AND EQUIPMENT FOR MAKING TENSION ANCHORS Filed July 7, 1966 Sheeti of 4 INVENTOR. Gamma Luqcnsm'o'm April 8, 1969 e. LAGERSTRUM METHODAND EQUIPMENT FOR MAKING TENSION ANCHORS Sheet i of 4 Filed July 7, 1966INVENTOR. Gunmm Laqcasmfim B Y April 8, 1969 G. LAGERSTRQM 3,436,923

METHOD AND EQUIPMENT FOR MAKING TENSION ANCHORS Filed July 7, 1966 Sheet4 of 4 Gannon. Laqenstn'o'm 34 Byqp r l 33 16 INVENTOR.

Copco Sweden Filed July 7, 1966, Ser. No. 567,800 Int. Cl. E02d /74;E21d 11/10 US. Cl. 6153.52

Aktiebolag Nacka, Sweden, a corporation of 9 Claims ABSTRACT OF THEDISCLOSURE A method and apparatus is provided for making a tensionanchor in the ground which utilizes drilling equipment forsimultaneously drilling the hole for the anchor and drawing down intothe hole a bundle of tension wires for the anchor by disposing the drawmember for the tension wires adjacent the drill bit, and by using atubular drill rod through which grouting is injected into the drill holeand around the tension wires simultaneously as the rod is withdrawn fromthe hole. In addition, the draw member is rotatable with respect to thedrill bit and rod, and the drilling equipment including the drill bit iscapable of drilling through rock as well as earth.

This invention relates to a method and equipment for making tensionanchors particularly in the ground. Such anchors are used for anchoringobjects such as sheet piling walls, building foundations, high tensionpower masts, suspension bridges, hydro power plant dams, or the like.The invention is particularly related to the pr0- vision of tensionanchors for heavy loads. Such anchoring is often carried out by means ofa bundle of heavy wires or cables which are anchored in the ground, forinstance in bed rock or in the overburden soil, in holes in which thewire or cable bundles are inserted and anchored by injection of groutingor similar material around the wires or the like. Tension anchors mayoften have to take a load of several hundred tons and in such cases ithas been found uneconomical to use tie rods since such rods for theseheavy loads are very expensive. It is in many cases more economical touse wire or cable bundles or bundles of other flexible members, such asflexible steel rods or steel bands or the like, which form a bundleanchored in a hole in the soil or in bed rock in which grouting or otherstabilizing material is injected. So far, bundles of wires or cableshave been inserted through a casing into a hole which, however, is anexpensive and cumbersome affair.

The present invention comprises making a tension anchor in the ground bydrilling a hole into the ground by means of drilling equipmentcomprising a tubular drill string carrying a drill bit, drawing a bundleof flexible tension members down into the hole by a draw member carrieddown by and preferably simultaneously with the drilling equipment, andinjecting grouting or similar material around at least a portion of saidbundle. Preferably a non-rotating draw member is used which is coupledto the drill bit in such a manner that the drill bit may rotate withoutrotating the draw member and carries the draw member and the tensionmembers down into the hole simultaneously during drilling whereupon theflexible tension members such as wires, cables, steel bands or thinsteel rods are fixed by injection of grouting. When the drill bit hasbeen drilled down through the overburden and prefreably some distanceinto bed rock the drill rod can be withdrawn and simultaneously groutingor the like is injected through the hollow drill rod to fill out theempty spaces in the bundle of wires or the like and also to fill outcavities in the ground around the hole so 3,433,323 Patented Apr. 8,1969 that a satisfactory anchorage is obtained. When the grouting hassettled the tension anchor is tested by means of hydraulic jacks inconventional manner.

In the accompanying drawings the preferred method and equipment formaking tension anchors is illustrated by way of example. FIG. 1 is adiagrammatic view illustrating in vertical section a portion of anexcavation for a building foundation surrounded by a wall of sheetpiling. FIG. 2. is a similar view and illustrates a completed tensionanchor and another tension anchor under construction. FIG. 3 is adiagrammatic elevation and partial section illustrating a feedingarrangement for wires used to form a tension anchor. FIG. 4 is a sideview partly in vertical section and illustrates means for guiding thewires into the hole, and FIG. 5 is an elevation of the equipment in FIG.4. FIG. 6 is a longitudinal section and partial side view of thedrilling end of the anchoring equipment according to the invention. FIG.7 is a section on line VI I-VII and FIG. 8 a section on line VIII-VIIIin FIG. 6. FIG. 9 is a transverse section on line IX-IX in FIG. 3.

In FIGS. 1 and 2 a cavity 1 is illustrated which provides space fordrill wagons or other drill carriages and for other equipment necessaryin connection with the construction of a building foundation. The cavity1 is surrounded by walls of sheet piling 2 which may or may not havebeen driven all the way down to bed rock 3. Said sheet piling may form acontinuous wall with openings for the tension anchors or the piles maybe placed at a distance from each other to provide openings in Ibetweenthe sheet piles for the tension anchors. The overburden which extendsdown from the original ground level 4 may comprise loose soil, sand,boulders, filling material or the like. 5 indicates boulders or blocksin the overburden soil 6. The cavity 1 is preferably excavated with asuitable digging machine while the tension anchoring goes on so that anupper row of tension anchors is positioned before the cavity is dug outto its final low level 7.

8 indicates a conventional feed bar for a conventional hammer drill 9which may preferably be a heavy hammer drill with separate rotationmotor. The hammer drill 9 operates on a shank adapter 10 which iscoupled to a hollow drill string comprising tubular drill rods 11 or asingle hollow drill rod 11 if the depth of the desired hole is not toolarge coupled together and to the shank adapter 10 by means of sleeves12. At the lower end the drill string 11 which is illustrated on alarger scale in FIG. 6 is provided with a drill bit 13 which may be ofsubstantially conventional design as regards the positioning of hardmetal inserts 14 which, however, are only carried out for being able todrill a comparatively short hole in rock, for instance three or fourmeters. The drill bit 13 is provided with flushing passages 15, 16 whichcommunicate with a large passage 17 in the drill string dimensioned sothat it can be used not only for the transportation of flushing fluidsuch as air, water or other flushing fluid to the drill bit but also forafterwards being used for transportation of grouting for injecting thehole and the surroundings of the tension anchor. The drill string issurrounded by a number of flexible tension members 18 which in theillustrated embodiment consist of heavy steel wires or cables, forinstance half inch steel calbles, which at the lower end are providedwith wire clamps 19 forming sockets 20 which in conventional manner maybe hydraulically secured by being pressed around the ends 21 of thecables or wires 18. The clamps 19 are inserted and fitted incorresponding recesses 22 in a draw member 23 which forms an annularbody or wire head of little less outer diameter than the diameter of thedrill bit 13 so that it can follow the drill bit 13 easily down into theground and into rock. The draw member 23 forms a central passage 24through which the drill string '11 may pass. A bushing 25 having anannular external flange 26 fits into the bore 27 in the draw member 23with ample clearance so as to permit said bushing 25 to rotaterelatively to the draw member and also to permit passage of flushingfluid and/ or grouting from the passage 17 into the draw member. Thelower shoulder of the flange 26 rests on a reinforced nylon ring 28 or aring of self-lubricating bronze or other material which cooperates witha tubular bushing 29 screwed into the lower end of the draw member 23,23 as indicated at 30. The bushing 25 has a square or otherwisenon-circular axial passage 31, FIGS. 6 and 8, in which thecorrespondingly shaped lower end 32 fits so that the drill string mayrotate the bushing 25 and thereby rotate the drill bit 13 which is screwthreaded onto the bushing at 33. The lower end 32 of the drill stringfits in the axial passage 31 in the bushing 25 in such a manner that thedrill string may easily be removed out of the bushing 25 by retractingthe drill string. The drill string end 32 has further flushing passages34 which communicate with flushing passages 35 in the bushing 25 andwith the clearance 36 lbetween the bushing 25 and the bushing 29 so thatsaid clearance may be well flushed with flushing medium during operationof the equipment. By flushing the clearance 36 the bearing formedbetween the bushing 29 and the flange 26 may be kept free from dirt anddebris.

The tension members 18 which may consist of wires or steel cables orflexible band steel or other similar flexible members pre-cut tosuitable length may be wound onto drums 37 which are fitted for rotationon brackets 38 secured to the lower end of the feed bar 8. 39 is a motorsuch as a compressed air motor which is in driving connection with theshafts 40 of the drums 37 so that the motor can rotate the drums. Theflexible members are guided over rollers 41 into a guide hopper 42 onthe feed bar which hopper consists of a split ring with a number ofaxial grooves 43, FIG. 9, one for each tension member .18, so that saidmembers are evenly distributed around the drill string 11. The hopper 42is divided in two parts hinged together to be able to be mounted on thebracket 38 and to receive the drill string and the tension member, asobvious from FIG. 9.

If a fairly large guide hopper is provided, as illustrated in FIGS. 4and 5, the tension members i18 may be fed into said hopper directly fromthe ground where they may just be put in order before drilling so thatthey may follow the draw member down into the hole as drilling proceeds.44 is a conventional drill steel guide of the type commonly used ondrill carriages of various types. The hopper 42 and the drill steelguide 44 may be carried by an axially adjustable or movable slidingmember 45 which may be operated into various axial positions by means ofa power cylinder in similar way as movable drill steel guides areoperable on feed bars for drill carriages. Such an arrangement makes iteasier to place the hopper 42 at ample distance above a couple ofchannels 46 or other structure which form supports for the anchor headson which the wire anchors are intended to rest. The channels 46 alsodistribute the tension over a number of sheet piles 2 of the sheet pilewall which it is desired to anchor.

47 is a lorry or other transportation means which carries the feed bar 8on brackets 49 which may be arranged to permit dumping of the feed barsdown on the lorry into substantially horizontal position. The lorry alsocarries pump equipment 50 for supplying flushing water and/or groutingthrough a hose 51 and a flushing head 52 which is rotatably disposed onthe adapter 10 and communicates with the passage 17 in the drill stringin a manner which is well known in this art. The number of wires orother tension elements 18 in tension anchors naturally varies accordingto the load for which the anchors are constructed and the dimension ofthe wires or other elements available in each case.

The method according to the invention is carried out in the followingmanner: The drill carriage or lorry 4'7 with the feed bar 8 is moved tothe position at the sheet piling 2 where it is desired to arrange thetension anchor. A drill bit 13 with a suitable draw member 23 fittedthereon is provided on the square end 32 of a drill string 11 and thedesired number of wires or cables are drawn from the drums 37 or fromthe ground where they lie ready for use and inserted in the recesses 22.The upper half of the hopper is closed and the draw member 23 with thewires is advanced through the hopper 42 and the tension members arebrought into position in the various grooves 43 and the wires arestretched. The sliding member 45 is then advanced towards the channels46 to a position substantially as illustrated in FIG. 4 and thereafterthe drill feed is advanced so that the drill bit and the draw member 23are moved down towards the ground pulling the tension members 18 throughthe guide hopper 42. As soon as the drill bit enters the ground flushingair or flushing water supply is provided through the passage 17 and therock drill 9 is started. The bit is now advanced through the overburden6 and drills through any boulders or other obstacles which areencountered, as illustrated in FIGS. 1 and 2. The drill bit is advanced,if desired, through the overburden down to bed rock 3, and such asuitable distance into bed rock as considered necessary for providing asafe anchorage. Usually the bit is drilled into bed rock 3 or 4 metersto be sure that it is bed rock and not a big boulder which has beenencountered. During the drilling operation the draw member 23 pulls thetension members 18 along down into the hole but the drill steel rotationis not transmitted to the draw member 23 due to the bearing arrangement28. When the drill bit and draw member have been carried down to adesirable depth, drilling is discontinued and flushing is alsodiscontinued and injection of cement grouting or other stabilizingmaterial from the pump equipment 50 starts while the drill string isstill in position in the drill bit 13. In order to provide a perfectanchor the drill string 13 is now slowly retracted and simultaneouslycement grouting, or similar material is injected through the passage 17into the cavities in and around the drill bit 13, the draw member 23 andthe flexible tension members 18 and also into cavities surrounding thehole produced by the drill bit 13, as is indicated at 53 in FIG. 2. Theamount of injected material naturally depends upon the condition of therock or ground and the tension which it is intended that the tensionanchor should be able to carry. Injection may be made just around thelower end of the tension members or all along said members or in certainareas as the case may be. It is also foreseen according to the inventionto provide a not illustrated casing around the tension members in whichcase the drill bit should be of slightly larger diameter than the outerdiameter of said casing and in such a way a concrete reinforced pile maybe produced which may be particularly of advantage in cases where theground may adversely affect the material of the tension members 18. Whencasing is used it is of course not necessary to draw the draw member andwire or cable bundle down simultaneously with drilling of the hole anddriving down of the casing. Instead after driving down a bit and acasing the drill string may be retracted and a special draw memberprovided thereon to which wires or other tension members are secured andwhich is then moved down through the casing to the bit by means of thedrill feed. Afterwards the casing may be retracted by means of the feedor special winches and injection is made through the drill string asdescribed or through the casing as described in my US. application Ser.No. 525,068 filed Feb. 4, 1966. When injection has been finished thedrill string is usually completely withdrawn and a suitable anchor head54, 55 may be provided at the upper end of the tension members 18 asindicated in FIGS. 1 and 2. After a few days when the injected materialhas settled sufiiciently the tension anchors are tested for the desiredtension with suflicient margin as may be stipulated for the particularjob.

The method above described and illustrated in the drawings as well asthe equipment illustrated should only be considered as examples and maybe modified in various different ways within the scope of the followingclaims. The method may for instance be used for various other purposesthan for anchoring sheet piling, such as for anchoring power line masts,suspension bridges, darn structures and casings for harbours and waterpower stations and other building structures.

What I claim is:

1. Tension anchor equipment comprising a drill string including a drillbit and a drill rod means arranged for transmitting rotation andpercussion energy to said drill bit and to be withdrawn from said bit, abundle of tension members surrounding said drill rod, a draw member inwhich said tension members are fixed, means for coupling said drawnmember to the drill string for advancing the draw member into the holebut not rotating the draw member, means for advancing said equipmentinto the ground, and means for supplying grouting around the tensionmembers.

2. Tension anchor equipment according to claim 1, in which the drillrods are tubular and provided with means for injection of grouting orthe like through said rods.

3. Tension anchor equipment according to claim 1, in which the drill bitis coupled to the draw member by a coupling which permits rotation ofthe bit relative to the draw member but which carries the draw memberforward together with the bit when the bit is fed forward by a drillfeed.

4. Tension anchor equipment according to claim 1, in which a number oftension members are wound on a drum carried by a drill feed and fed fromthe drum into the hole to form an anchor together with the draw member.

5. Tension anchor equipment according to claim 1, in which a guidehopper having a number of axially extending internal grooves for guidingtension members is provided at the forward end of a drill feed.

6. Apparatus as described in claim 1 in which each of said tensionmembers includes a socket and a pertaining coupling head pressure fittedthereon at one end, said coupling head being formed to engage said drawmember.

7. A method for making a tension anchor in the ground by means ofdrilling equipment including a tubular drill string carrying a drillbit, the steps which comprise drilling a hole into the ground by meansof said drilling equipment, surrounding said drill string by a bundle offlexible tension members, simultaneously drawing said bundle of flexibletension members down into said hole by a draw member disposed adjacentsaid bit, and injecting grouting around at least a portion of saidbundle.

8. A method of making a tension anchor in the ground by means ofdrilling equipment including a tubular rotatable drill string carrying adrill bit capable of penerating rock, the steps which comprise drillinga hole into the ground by means of said drilling equipment, surroundingsaid drill string with a bundle of flexible tension members, drawingsaid bundle of flexible tension members down into the hole by a drawmember rotatable relative to said drill string and said drill bit, andsaid draw member being carried down by said drilling equipmentsimultaneously with said drill bit during the drilling of said hole.

9. A method for making a tension anchor in the ground by means ofdrilling equipment including a tubular drill string carrying a drill bitand a drill wagon carrying a feed bar for said drill, the steps whichcomprise drilling a hole into the ground by means of said drillingequipment, providing one or more reels on said drill wagon on which anumber of flexible tension members are wound for being fed in one ormore bundles into said hole as drilling proceeds, simultaneously drawingsaid bundles of flexible tension members down into said hole by a drawmember disposed adjacent said drill bit, and injecting grouting aroundat least a portion of said bundles.

References Cited UNITED STATES PATENTS 1,805,265 5/1931 Taussig 6153.6

3,299,644 1/1967 White 6l39 3,363,422 1/1968 Turzillo 6139 X FOREIGNPATENTS 1,243,359 8/1960 France.

JACOB SHAPIRO, Primary Examiner.

U.S. Cl. X.R. 52156; 61-39,

